Washington – Despite a downward trend in asbestos concentration levels over the course of nearly three decades, many workers in construction, automotive repair, manufacturing and other industries inhaled asbestos at heightened levels, according to a recent report.

Researchers from scientific consulting firm Cardno ChemRisk analyzed data collected by OSHA between 1984 and 2011. They found that some air samples were 875 times higher than OSHA’s limit for workplace exposure to asbestos fibers per cubic centimeter.

Workers who inhale asbestos may experience lung damage and develop scar-like tissue and diseases such as mesothelioma, OSHA says. Asbestos fibers are too small to be seen.

The study was published online May 16 in the journal Regulatory Toxicology and Pharmacology.